1. Field of the Invention
The present invention relates to a zoom lens, and an image pickup apparatus using the same.
2. Description of the Related Art
In recent years, instead of a silver-salt film camera, a digital camera in which, an object is photographed by using an image pickup element such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) has become a mainstream. Furthermore, there are several categories of digital cameras in a wide range from a high-function type for professional use to a compact popular and widely-used type.
From among the digital cameras in the wide range, with the popular and widely-used type digital camera, a user seeks to enjoy photography readily, anywhere at any time with a wide range of scenes. Particularly, since a slim digital camera can be accommodated easily in a pocket of clothes or a bag, and can be carried conveniently, such digital camera has been preferred. Due to this, further small-sizing of an image pickup lens system has been sought.
Moreover, with regard to a capture area, user seeks to capture a wide area. Therefore, a taking lens system having a wide angle of field characteristic such as a taking lens system with a wide angle of field, where the an angle of field at diagonally opposing corners is more than 70° has been sought. Moreover, with regard to a zooming ratio, an image pickup lens system having the zooming ratio of more than five times has been sought.
As a zoom lens having a comparatively wide angle of view, a zoom lens which includes in order from an object side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a negative refractive power, and a fourth lens unit having a positive refractive power has been known (Japanese Patent Application Laid-open Publication No. 2010-54722 and Japanese Patent Application Laid-open Publication No. 2003-131130).
A zoom lens disclosed in Japanese Patent Application Laid-open Publication No. 2010-54722 is a zoom lens having the zooming ratio of five times. In this zoom lens, a second lens unit includes three lenses in order from an object side, namely, a positive lens, a positive lens, and a negative lens. Whereas, a zoom lens disclosed in Japanese Patent Application Laid-open Publication No. 2003-131130 is a zoom lens having the zooming ratio of three times. In this zoom lens, a second lens unit includes three lenses in order from an object side, namely, a positive lens, a negative lens, and a positive lens.